1. Field of the Invention
The invention broadly relates to a method and apparatus for manufacturing keystone type piston ring structures which are typically employed as compression rings in engines and utilized in a wide variety of engine applications. The objective of the ring structure is to effect a seal in the space between an associated piston and liner to prevent the high-pressure combustion gases or the air charge from escaping down the liner during the compression or power strokes; to transmit head energy from the piston to the cooled cylinder liner; and to absorb a certain part of the fluctuations of the piston side thrust.
2. Description of the Prior Art
Some internal combustion engines have compression rings with the bottom wall or both the bottom and top walls beveled, making the ring thinner at the inside than at the ouside diameter. The associated groove in the piston for receiving the ring is machined to the same general shape. The gas pressure acting on the top wall of the ring owing to the bevelled bottom surface, produces an additional force pressing the ring outwardly against the cylinder wall and helping to adequately effect the desired seal.
On the other hand, at each reversal of the side thrust of the piston, the ring slides slightly into the associated groove, is pressed against the upper groove wall, crushes the carbon which is deposited on it, and keeps the ring from sticking.
It is an objective of the present invention to produce a piston ring structure for a fluid pressure system wherein the sealing relationship of the ring and the associated piston is improved to effect a gas-tight seal.
It is another object of the invention to produce a piston ring structure wherein line-to-line contact is achieved between the piston ring and the peripheral groove in the associated piston to prevent combustion gases, for example, in an internal combustion engine from passing to the crankcase, and oil from passing to the combustion chamber in excess quantities.
Still another object of the invention is to produce a piston ring structure wherein at least one wall thereof is inclined inwardly and of a curved cross-section to thereby cooperate with a suitably shaped groove in an associated piston to effect a line-to-line contact between the curved surface of the ring and the outer edge of the groove in the piston.
Another object of the invention is to produce a piston ring having at least one inwardly inclined wall of curved cross-section which may be readily and economically manufactured.
A specific object of the invention is to provide a method and apparatus for making a piston ring having at least one inwardly machined wall of a curved cross-section.